Modern motor vehicles often include one or more driver information and driver assistance systems (hereinafter referred to as in-vehicle information systems) that provide a wide variety of information and entertainment options to occupants in the vehicle. Common services that are provided by the in-vehicle information systems include, but are not limited to, vehicle state and diagnostic information, mapping and navigation applications, hands-free telephony, radio and music playback, and traffic condition alerts. In-vehicle information systems often include multiple input and output devices. For example, traditional buttons and control knobs that are used to operate radios and audio systems are commonly used in vehicle information systems. More recent forms of vehicle input include touchscreen input devices that combine input and display into a single screen, as well as voice-activated functions where the in-vehicle information system responds to voice commands. Examples of output systems include mechanical instrument gauges, output display panels, such as liquid crystal display (LCD) panels, and audio output devices that produce synthesized speech.
Three-dimensional (3D) graphics methods have been widely used in different driver assistance and driver information applications. One typical example is navigation systems based on 3D maps. 3D maps depict visualizations of the real world scenes that include depictions of the height and structure of terrain and objects in a realistic manner so that the driver could attempt to match the synthetic appearances of rendered 3D objects in the map with those of real-world 3D objects that he observes through the wind shield. Compared with traditional two-dimensional (2D) maps, 3D maps are considered to be more helpful for easy driver orientation and fast location recognition. For example, 3D mapping and navigation services are provided by multiple online and offline services including services offered by Apple, Google, and Nokia.
However, 3D graphics in mapping and navigation applications can include a drawback when a driver wishes to review a route that is drawn on the map. The route graphic typically follows a path along one or more roads or trails, which are located at ground level in many routes. The presence of 3D objects around the route, such as graphical objects corresponding to 3D buildings, terrain, or other features, can block the route at various viewing angles in the 3D virtual environment. Existing techniques to improve the visibility of the 3D navigation route either require the operator to reorient the 3D view to avoid occluding objects, or remove the 3D objects or apply partial transparency to the 3D objects to provide a view of the route. These techniques reduce the level of realism in the 3D environment. Consequently, improvements to 3D visualization techniques for in-vehicle information systems that improve the visibility of navigation routes in the presence of occluding 3D objects would be beneficial.